*124*P# – set this device priority P (1-3) or 0 to disable, doesn’t seem to work

*125# – route SMS here
*126# – route MMS here

These are all USSD codes which you run on the phones to configure the call routing. I couldn’t get the priority to work, it maybe isn’t supported by simplytel (Drillisch) as a reseller of o2, not sure. I got this info here.